1. Field of the Invention
The present invention is related to the field of application equipment for distributing dry material onto a field or the like and, more particularly, to an automatic output monitoring system for an air transport material delivery system.
2. Description of the Related Art
One method for spreading seeds or powder type fertilizers onto a field is to use a pressurized air transport material delivery system mounted to a tractor. The seed, fertilizer or other dry material is fed from a storage hopper to a manifold via a series of holes and funnels. In the manifold, the material is mixed with pressurized air from a turbine or compressor and sent down a set of horizontal delivery tubes from which the material exits at a high rate of speed. At the exit end of each tube, a metal deflector is positioned that redirects the material impinging on its inner surface downwardly, and disperses the redirected material evenly on the ground.
The air transport material delivery system may have up to 20 tubes, each of a different length. They are usually spaced evenly along a boom carried by the tractor in order to cover the most ground. The shortest tubes terminate immediately behind the tractor and the longest tubes generally extend out about 35 feet on either side of the tractor. In the case of a system with 20 tubes, ten tubes will extend out on each of the left and right sides.
A common problem encountered with machine-mounted air transport material delivery systems is that the funnels, orifices and tubes can become partially or completely blocked during operation. When this occurs, the driver of the machine may not realize there is a problem because the dust and small particle size make it very difficult for a loss in spread pattern to be visually perceived. Furthermore, the driver's position does not allow him or her to see the entire boom, but only the outermost deflectors. At a result, even if the spread pattern of the outermost deflectors could be visually monitored, blockage of the innermost deflectors would still go undetected. When blockage occurs, the driver may, without being aware of the existence of the problem, thereafter cover several acres while providing inadequate dry material distribution.
A system described in U.S. Pat. No. 5,831,542 for monitoring air seeder blockage uses a flexible piezoelectric element placed directly in the air/seed stream. Seed flow is detected on the basis of seeds striking the piezoelectric element, with seed flow rate being determined by counting the number of seed strikes. However, the piezoelectric element is susceptible to damage due to the continual bombardment thereof by the seed stream and may also be subject to other drawbacks and damage.